Citroen C4 Lack of Power

[cenk]

Hi everyone,
I have a 2011 Citroen C4 1.6 VTI auto, and I'm in trouble with my car, there is a lack of power both on petrol and LPG, it feels more when going uphill, slowing down too much, straight road acceleration is not satisfactory, fuel consumption is also seems high, i took my car to the authorized technical service, and gives the following error codes;

BVA_AT8 Section : U1003
MEV17_4_2 Section : U2000, U2118, P0420
ABS Section : C1510, U2000, U1318

and Mechanic says it's normal, these error codes are insignificant, VTI engines are known for low performance
can you help me with this problem please?

PS: There's a non-priority issue: I don't know if it's related with other issues but steering is hard also.
My Car's VIN: VF7**************[VIN obfuscated, can be read by forum staff]

[cenk]

urgent @GiveMeABreak help needed
for example while driving a slight uphill, 1500 rpm, and fuel consumption a whopping 15 liters,
and pressing gas pedal makes fuel cons. worst, while rpm not increase, car choking,
car decatted, spark plugs changed 1 week ago, and symptos persists